Here's how I've done it before:
- pencil sketch
- Adobe Illustrator -> select image -> Live Trace. I start with the comic setting. Tweak threshold, blur, and path to get the image you want. Don't click strokes; fills scale much better.
- Convert to Live Paint. Coloring is trivial.
In this image, my Live Trace wasn't quite closing some gaps so I went back and redrew some lines. The white dots are touch ups with Fireworks, post-scan, to make the Live Trace more accurate. There's probably a way to do this with Illustrator, but I'm a novice.
(Please refrain from upvoting based on this incredible display of fine art.)
I've tried a Wacom Graphite 2 drawing tablet but it was a little slippery and sensitive and required some kind of drawing adjustment for me to get used to. Plus, I couldn't draw as fast as I can with pencil and paper.